The present invention relates to a diesel fuel shut-off device for a diesel engine to prevent air from being ingested into the fuel system when the fuel tank is empty.
Diesel fuel systems of motor vehicles historically have had problems when they run out of fuel and air is ingested through the fuel pump into the fuel line. The ingested air in the fuel line causes rough starting of the engine. Even if the vehicle operator adds diesel fuel to the fuel tank, the engine may not start again as a result of the air ingested in the fuel line. In some cases, the air must be drained from the fuel supply rail on the diesel engine. Draining of the air from the fuel rail is effected by a service attendant using bleed valves on the fuel rail.
An object of the present invention is to provide a fuel shut-off device for a diesel engine that prevents air from being ingested into the fuel system when the fuel tank is empty.
The present invention provides in one embodiment a fuel shut-off device and method for a diesel fuel tank of a motor vehicle to discontinue fuel flow to a fuel pump before air can be ingested into the fuel system when the fuel tank is near empty. A fuel control valve is controlled by diaphragm between open and closed valve positions relative to a valve seat depending on fuel level in the fuel tank. The fuel control valve is moved to the closed position relative to the valve seat when the fuel level in the tank is at a predetermined low (near empty) level to provide insufficient fuel to the fuel pump to maintain engine operation so as to cause the engine to stop operation before air is ingested in the fuel system. The fuel control valve is moved to the open position relative to the valve seat when the fuel level in the tank is above the predetermined low (near empty) level.
In an embodiment of the invention, the fuel shut-off device comprises a spring biased fuel control valve cooperably disposed relative to a valve seat to control fuel flow from the fuel tank to the fuel pump. The fuel control valve is actuated between open and closed positions relative to the valve seat by movement of a diaphragm controlled by pressure of fuel in a control chamber and a valve spring. The control chamber includes an inlet orifice communicated to the fuel tank and an outlet orifice communicated to the fuel pump. An inlet orifice valve is disposed in the fuel tank to open or close the inlet orifice of the control chamber to the fuel tank depending upon fuel level in the fuel tank. The inlet orifice is open to the fuel tank when the fuel level is above a predetermined low (near empty) level such that the diaphragm is caused to move toward the fuel control valve to move it to the open position relative to the valve seat against bias of the spring. The inlet orifice is closed to the fuel tank when the fuel level is at the predetermined low level such that the diaphragm is caused to move in an opposite direction by the fuel control valve and the biasing spring to allow the biasing spring to move the fuel control valve to the closed position to thereby terminate fuel flow to the fuel pump. Closure of the fuel control valve when the fuel level is at the predetermined low (near empty) level prevents the fuel pump from drawing sufficient fuel to maintain engine operation, thereby causing the engine to stop before air can be ingested into the fuel pump.
In a particular embodiment of the invention, the inlet orifice valve comprises a float that is disposed in the fuel tank and movable with fuel level therein so as to close the inlet orifice of the control chamber when fuel level is at the predetermined low level.
In another embodiment of the invention, the inlet orifice valve comprises a solenoid actuated valve that is electrically actuated to close the inlet orifice in response to the fuel level being at the predetermined low level. A fuel level sensor is provided in the fuel tank to provide a signal to actuate the solenoid actuated valve to close the inlet orifice of the control chamber when the fuel level is at the predetermined low level.
The above objects and advantages of the invention will become more readily apparent from the following description taken with the following drawings.